Although the folks at Cobra Automotive make their own equal-length headers, shop president Curt Vogt considered our needs and budget and admitted that our Mustang didn't need this rather costly setup.
He suggested that we order a set of Hooker headers—part No. 6901, $498.95 at Summit Racing—but added that any store-bought headers will need some modification to be usable in a serious race car.
Despite how beautiful those new headers may look, Curt said, their coating won’t hold up in a racing environment. His advice: Get the headers recoated by a specialist. We've worked with Swain Tech Coatings for decades and have always received terrific service, so that was our obvious choice for the job.
Curt explained that rust inside the header tubes can cost power—based on his experience, anywhere from 5 to 15 on an engine like ours—so he recommended coating the insides as well as the outsides.
Next, he told us that we could cut off the heat riser tube that was wrapped around one of the header pipes. We won’t be using it, so it would have just gotten in the way and added weight.
He also warned that mass-produced headers aren't always flat on the flange face, so we would need to test this with a straightedge. Sure enough, while one side was perfect, the other was a little off. A minute or two on our large shop belt sander solved this problem.
Since our engine uses World Products Windsor Sr. iron heads, Curt also urged us to check the spark plug access before sending out the parts for coating.
He was right again. Without modification, our headers’ spark plug angles would have caused the plugs on the left cylinder bank to be blocked.
Curt suggested that we mark the offending areas, then heat and dimple them. But don’t hit the headers directly with a hammer, he cautioned; instead, hammer a piece of the correct-diameter pipe (used at the correct angle) to massage the header tubes.
These headers end in 3-inch collectors, and Curt recommended that we cut them off. He told us to design a slip-fit pipe to fit the outside of the header and then take that to an X-pipe, not an H-pipe—also attached via a slip-fit.
His reason for this modification: Collector gaskets always leak with racing use. Plus, the exhaust system should be designed for quick removal to allow for repair and service.
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Comments
How much would a set of custom welded headers cost? How hard would it have been to roll your own with a header kit and a tig. I was with you until you bent them to access the spark plugs. Yes I know the it has a minimal if any effect on performance but it just looks bad to me. Call it header OCD on my part. And besides I would have liked to read your impressions of trying to build your own from one of those header kits I see used in builds. That would have been an interesting read.
There has to be a manufacturer out there that makes a header that you don't have to bend to fit. To me that is poor design on the manufacturers part. Even if it cost another couple hundred bucks to get a properly engineered set to me it would have been my choice as every time you open the hood people will see the deformed pipes. (That OCD thing I have again).
I think once they get back from coating, they'll look like the were built to be like that.
I think the biggest thing is with the advancements in spark plug longevity, most street driven vehicles with headers probably won't see a plug change during the original installers ownership, so ease of accessibility for maintenance probably rates low priority during the designing phase.
FMB42
Reader
3/25/21 5:21 p.m.
Store-bought headers are both great and not so great in my limited header experience ('65 GTO and '67 SBC powered Skylark). But, as Djg above says, greatly extended spark plug life makes a big diff in some ways. Note: store-bought headers were a life saver on many RVs of the 70s, 80s, and 90s,etc (cracked OEM cast iron exh manifolds were a very common RV problem back then).
If rust inside the header tubes can cost power anywhere from 5 to 15 how much would large dents in the tubes cost?
In reply to L5wolvesf :
https://www.bing.com/videos/search?q=youtube++dented+header+test&docid=607988612658657263&mid=8550742B373685B9D5618550742B373685B9D561&view=detail&FORM=VIRE
"Collector gaskets always leak in racing use" is three words too many 
I've had headers with the little rings on the head side "for extra sealing" turn out to have the rings miss common header gaskets at the corners. Need to grind the weld ring down a little for a nice V-notch, weld it larger, then file it flat again.
Collector gaskets work fine if you get quality gaskets and quality clamping ring on both the header/collector and the pipe. The problem is cheep headers are cheep and this is just one more area where you get what you pay for.
With all the mods they made to those headers better quality ones may have actually been cheeper/better.
L5wolvesf said:
If rust inside the header tubes can cost power anywhere from 5 to 15 how much would large dents in the tubes cost?
I have never heard of that before but it has me thinking that it would have been cheeper to just get a decent set of stainless steal headers and do the WD40 trick to get that cool gold bronz finish. Versus what ever it will cost to have cheap headers ceramic coated. Both inside and outside.
How do the ceramic coating people know that they get a good coating inside a header? Run an endoscope down it? It would be interesting to see how that process is done.
Sonic
UltraDork
3/26/21 8:28 a.m.
If you can't dip them then how about pouring the coating in the tubes then covering all the openings and rolling the headers around to all possible angles in your hands so that it spreads around, then uncover the openings and drain (into the other header)
I must be out of touch, but nearly $500 for a set of headers isn't cheap. But I am probably out of touch.
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